The present invention relates to a system and method for improving the quality, clarity, and intelligibility of devices such as hearing aids, voice messaging systems, and telephone switches by adding even harmonic distortion to audio signals.
The process of adding harmonic distortion, particularly even harmonic distortion, to improve the clarity of audio signals is known in the field of audio signal processing. U.S. Pats. Nos. 3,828,133, 4,150,253, 5,133,014, and 5,359,655 disclose processes in which the audio signal is divided into two signal paths. One signal path is utilized to generate the harmonic distortion which is then combined with the other signal path to produce and enhance the audio signal. The combined signal is perceived to be of higher quality when even harmonic distortion is used. This is particularly true when the audio signal is a voice signal.
Processes for producing even harmonic distortion have been employed in wide bandwidth (20 Hz to 20 KHz) signal processing, i.e., high fidelity audio signals. For example, U.S. Pat. No. 5,424,488 discloses a harmonics generator which may be used to improve the sound quality of electronic audio equipment.
In the past, hearing aids have used equalization to compensate for hearing losses. However, it is desirable to provide a system and method for harmonic enhancement of hearing aids because the enhancement provides a richer, more detailed sound to the user.
It is also desirable to provide a system and method for harmonic enhancement of mechanisms that limit the human perception of audibility such as telephone systems, cellular phone systems, low bit rate audio, perceptually encoded low bit-rate audio, and low band-width audio. For instance, it is desirable to provide harmonic enhancement to overcome hashing noises commonly found in voice messaging systems and telephone switches employing data compression methods.
Accordingly, it is an object of the present invention to provide an even order harmonic enhancement system and method for improving audio clarity of hearing aids and other communication devices such as voice messaging systems and telephone switches.
It is another object of the present invention to provide a first order (or higher) even harmonic generator enhancement system and method for improving audio clarity of hearing and other communication systems.
In carrying out the above objects and other objects, the present invention provides a method of improving clarity of an input signal for a hearing aid. The method includes selecting frequencies of the input signal for processing and adding even harmonic distortion, preferably, of at least the second order, to the selected frequencies.
A system for implementing the method according to the present invention is also disclosed. Other methods and systems are also disclosed in accordance with the present invention.
These and other features, aspects, and embodiments of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings.